Computer Chess Club Archives




Subject: Re: When to do a null move search - an experiment

Author: Robert Hyatt

Date: 20:25:59 04/29/04

Go up one level in this thread

On April 29, 2004 at 16:17:34, Ed Schröder wrote:

>On April 29, 2004 at 14:44:47, Robert Hyatt wrote:
>>On April 29, 2004 at 09:28:53, Ed Schröder wrote:
>>>On April 29, 2004 at 07:37:23, Vincent Diepeveen wrote:
>>>[ snips ]
>>>>>This is all very poor Vince, I assume you don't play much with nowadays top
>>>>>programs. From 1982 to 2001 Rebel won its games by positional understanding and
>>>>>not by search and Rebel lost its games because it was outsearched. Today Rebel
>>>>>isn't outsearched at all, it now loses its games because the current top
>>>>>programs have a better positional understanding than Rebel.
>>>>>You should have a good look at the current tops, the positional progress has
>>>>>been great the last years. To me it all seems to indicate (provided your search
>>>>>is okay) the only way to make progress is to improve on chess knowledge. But
>>>>>what's new, I already came to that conclusion in 1986 after some intensive talks
>>>>>with Hans Berliner.
>>>>What i mean is Ed, is that you would not have accomplished the great results
>>>>with Rebel which you managed, had you just searched with a fullwidth search +
>>>>bunch of checks in qsearch.
>>>No of course not, brute force is silly, Rebel since day 1 has been a selective
>>>program. But I am getting your point, in the days before the nullmove was
>>>discovered Genius and Rebel had the best (static) selective search, a dominant
>>>factor in their successes, is that what you meant to say? If so, it is true.
>>>If only Frans had kept his mouth shut to Chrilly (Chrilly leaking nullmove in
>>>the ICCA journal) it is very likely Fritz would been the next Richard Lang still
>>>dominating all the rating lists and WCC's for the last decade. But Frans didn't
>>>and then all bets were off.
>>Chrilly wasn't the one that started the null-move search stuff.  Don Beal was
>>the first I recall reading although Murray Campbell also wrote a paper on the
>>idea.  I will try to flip through the surviving Cray Blitz source listing to see
>>exactly when null-move was added to it.  All I remember is Burton Wendroff
>>(Lachex) sending me a copy of Murray's paper and saying "try this". (this
>>happened while I was preparing for an ACM or WCCC event).  Of course I am
>>talking about R=1, non-recursive, as it was defined "in the good old days".. :)
>Actually Don Beal told Frans about nullmove in Cologne 1986, Don at that time
>only used nullmove in QS. Don did not use nullmove as we know it today, that
>came after Chrilly's article.

Yes, but Campbell defined "the null-move observation" exactly as it is used
today (no move played, reduce depth, if it fails high, then let the search fail
high with no more searching.)  He even suggested that R=2 needs serious testing.

Chrilly's main advancement was using the null-move observation to detect threats
and extend the search when the condition was met.  I don't know of anyone that
really does this today.  I did it back around version 9, but stopped due to the
high cost and low return...

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